Cook onions in hot oil in a large skillet over low heat, stirring often, 30 to 35 minutes or until onion is caramel, Stir in salt and set mixture aside, Unfold pastry; fit into a 9-inch square tart pan, Bake at 400° for 15 to 20 minutes or until browned, Remove from oven,______, Top with caramelized onions, Sprinkle with Parmesan cheese, Bake 5 more minutes,